Temperature-dependent growth morphology of a semiconductor-metal interface: Ge/Ta(110)

The Ge/Ta(110) interface is studied as a function of Ge coverage and temperature (25≤T≤980 °C) using synchrotron-radiation photoemission and low-energy-electron diffraction (LEED). Valence-band and core-level results indicate that no intermixing of the Ta or Ge atoms occurs across the interface at room temperature but that Ge/Ta interface states are formed. Comparison of the photoemission data with LEED results suggests that the low-coverage chemisorbed configuration evolves with coverage into a highly disordered Ge overlayer. Heating induces formation of a reacted overlayer with average composition ${\mathrm{TaGe}}_2$. However, the initial reactive interdiffusion occurs at lower temperatures than those reported for the formation of bulk tantalum germanides. A model is presented for the morphology of the reacted layer.